The present invention relates to an improvement of the characteristic of a distributed feedback semiconductor laser (hereinafter referred to simply as "DFB laser").
The DFB laser has the construction which has, in a light emitting layer or an adjoining layer, periodic corrugations serving as a diffraction grating to thereby equivalently introduce periodic refractive index variations in the layer.
Such a conventional laser has a distorted output during modulation or undesirable influence on a single wavelength operation.